This POTD was inspired by a morning report I was present for in Shock Trauma. The case was a 40ish male involved in an MVA. Patient was "shan scanned" for blunt traumatic mechanism. Surgeons saw a ton of free fluid on the scan and took patient directly to the OR. No intra abdominal injuries nor hemoperitoneum were found in the OR. It was later discovered, the patient had a drinking history w/ a cirrhotic liver and the free fluid initially assumed to be blood was actually acetic fluid.
PODT: Free Fluid in the Belly
So you have a trauma patient with a history of alcoholic cirrhosis. Your FAST is positive but your are unsure whether the free fluid you are seeing is blood from the trauma or the patient's chronic ascites.
You Pan-CT the patient and again all you see is free fluid, unable to tell if what you're seeing is blood or ascites. Your vitals, labs may help guide you. You can also potentially do a diagnosis parenthesis if there is a big enough fluid pocket but this is a very invasive procedure.
What you should do, is look at the Hounsfield Units (HU)!
HU are built into most imaging software and can be used to measure the radiodensity of the material on CT to help distinguish various structures.
Uncoagulated blood typically measures 30 to 45 HU
Clotted blood measures higher at 60 to 100 HU
Ascites/ Plasma measures around 0 to 20HU
So there you have it. You can use HU while looking at your CT images to help you determine whether your trauma patient is bleeding into their belly or what your seeing is more chronic.
TR Adam
An example of hemoperitoneum
An example of hemoperitoneum
An example of plasma/ ascetic fluid
An example of plasma/ ascetic fluid